Research on the reaction mechanism of key active groups in biomimetic antioxidant hydrogel for inhibiting coal spontaneous combustion

Coal spontaneous combustion will reduce the fuel quality and produce harmful gases. To develop an environmentally friendly material to regulate the reactivity of coal fuel, this study developed a green, biomimetic antioxidant hydrogel inhibitor. Using proanthocyanidins modified with gallic acid as the active ingredient and a hydrogel as the carrier, a biomimetic antioxidant hydrogel inhibitor was prepared. Programmed heating experiments examined gas release at different inhibitor dosages. The inhibition rate increased with dosage and then leveled off. The optimal dosage was 5 wt%, considering both effectiveness and cost. At this level, oxygen consumption and the release of CO, CO 2 , C 2 H 4 , and C 2 H 6 decreased significantly. FTIR analysis showed that treated coal had higher levels of –CH 3 , –CH 2 , C–H, –OH groups than raw coal, while C=O content in the late oxidation stage decreased by 7.78 %. Spearman correlation analysis revealed strong links between these groups and gas release, with the strongest link (0.92) between C=O and hydrocarbon gases. Using Gaussian software, simplified coal molecular models were built. Results showed that oxygen-rich areas are electron-rich, while hydroxyl hydrogens and carbonyl carbons are electron-poor. Further calculations based on ΔG and ΔH values showed that the inhibition pathway is thermodynamically more favorable than the oxidation pathway. Therefore, the hydrogel reduces the reactivity of the coal oxidation process by blocking the gas generation pathway driven by free radicals.